Summary: The proposed project is aimed at developing a novel class of drugs against chronic diseases associated with old age. Such agents act by inhibiting a newly discovered regulatory pathway that endows senescent cells with disease-promoting paracrine activities. Senescent cells, which arise as a result of aging or stress response, have been found to secrete multiple proteins implicated in age-related diseases, including Alzheimer's disease, amyloidosis, atherosclerosis, chronic renal disease, arthritis and cancer. These proteins are upregulated in response to the expression of cyclin-dependent kinase inhibitor (CDKI) proteins, which mediate cell cycle arrest in senescence and other physiological situations. High-throughput screening, followed by a battery of biological assays, resulted in the identification of several related compounds that inhibit disease-promoting activities of senescent cells. These molecules, designated SNX2-class compounds, do not interfere with the essential role of CDKI in cell cycle arrest, but they block the induction of disease-associated genes in CDKI-arrested cells. These compounds also block the development of senescent morphology in drug-damaged fibroblasts and inhibit the secretion of anti-apoptotic factors by CDKI-expressing cells. SNX2-class compounds may be considered as prototype drugs against the disease-promoting effects of cell senescence. The molecular target of SNX2-class compounds is presently unknown. Its identification is essential both for understanding the mechanism of action and for lead optimization of SNX2-class compounds. The goal of this Phase I SBIR is to identify the most likely molecular target of SNX2-class compounds. Aim 1 of the proposed strategy is based on the selection of proteins, increased expression of which is associated with phenotypic resistance to SNX2- class compounds. Aim 2 is to identify signal transduction pathways affected by the compounds, by determining the effect of the compounds on cellular protein kinase and gene expression profiles. Proteins identified in Aim 1 and key regulators of signal transduction pathways identified in Aim 2 will then be screened by RNAi knockdown, to determine which of these proteins are required for the induction of transcription by CDKI. A protein with such properties will represent the most likely molecular target of SNX2-class compounds. Its identification should facilitate the development and optimization of new drugs for the chemoprevention or therapy of age-related diseases. Relevance: With the aging of the American population, chronic age-related diseases, such as Alzheimer's disease, atherosclerosis, chronic renal disease and cancer, are becoming an increasingly greater burden on the society. There is a great need for developing novel pharmaceuticals that would be efficient against these largely incurable diseases. Senex Biotechnology, Inc. is a startup drug discovery company that targets a newly discovered biological regulatory pathway, which causes increased production of proteins implicated in different age-related diseases. Senex has discovered drug-like small molecules that block this disease-promoting pathway. The goal of this Phase I SBIR application is to identify the molecular target of these novel compounds. Such identification should make it possible to develop a new type of drugs that will slow down or reverse the development of Alzheimer's disease or other age-related diseases. [unreadable] [unreadable] [unreadable]